The purpose of this core is to distribute tester strains and give advice to users of the Ames Salmonella Mutagenesis assay. The Salmonella/liver microsome assay for mutagenicity, developed by Dr. Ames and his students, is a rapid, efficient way to test chemicals for their ability to mutate DNA. It is in use by more than 3000 government, academic, and industrial laboratories throughout the world, including most major pharmaceutical and chemical companies. New Salmonella strains are developed which can be used to diagnose the induction of specific types of gene mutations. The facility houses the storage and maintenance of the over 5000 Salmonella typhomurium and Escherichia coli strains developed in the laboratory and distributes Salmonella strains to any laboratories who require them. About 25 requests are processed each month. In addition, the facility provides training on the use of the assay in the laboratory and through communications. Approximately 15-20 students used the expertise from this Core for their science fair projects.